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DOE OSTI2013

A tiered approach for the human health risk assessment for consumption of vegetables from with cadmium-contaminated land in urban areas

Consumption of vegetables that are grown in urban areas takes place worldwide. In developing countries, vegetables are traditionally grown in urban areas for cheap food supply. In developing and developed countries, urban gardening is gaining momentum. A problem that arises with urban gardening is the presence of contaminants in soil, which can be taken up by vegetables. In this study, a scientifically-based and practical procedure has been developed for assessing the human health risks from the consumption of vegetables from cadmium-contaminated land. Starting from a contaminated site, the procedure follows a tiered approach which is laid out as follows. In Tier 0, the plausibility of growing vegetables is investigated. In Tier 1 soil concentrations are compared with the human health-based Critical soil concentration. Tier 2 offers the possibility for a detailed site-specific human health risk assessment in which calculated exposure is compared to the toxicological reference dose. In Tier 3, vegetable concentrations are measured and tested following a standardized measurement protocol. To underpin the derivation of the Critical soil concentrations and to develop a tool for site-specific assessment the determination of the representative concentration in vegetables has been evaluated for a range of vegetables. The core of the procedure is based on Freundlich-type plant–soil relations, with the total soil concentration and the soil properties as variables. When a significant plant–soil relation is lacking for a specific vegetable a geometric mean of BioConcentrationFactors (BCF) is used, which is normalized according to soil properties. Subsequently, a ‘conservative’ vegetable-group-consumption-rate-weighted BioConcentrationFactor is calculated as basis for the Critical soil concentration (Tier 1). The tool to perform site-specific human health risk assessment (Tier 2) includes the calculation of a ‘realistic worst case’ site-specific vegetable-group-consumption-rate-weighted BioConcentrationFactor. -- Highlights: • A scientifically-based and practical procedure has been developed for assessing the human health risks from the consumption of vegetables. • Uptake characteristics of cadmium in a series of vegetables is represented by a vegetable-group-consumption-rate-weighted BioConcentrationFactor. • Calculations and measurement steps are combined.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

Metal uptake by homegrown vegetables – The relative importance in human health risk assessments at contaminated sites

Risk assessments of contaminated land often involve the use of generic bioconcentration factors (BCFs), which express contaminant concentrations in edible plant parts as a function of the concentration in soil, in order to assess the risks associated with consumption of homegrown vegetables. This study aimed to quantify variability in BCFs and evaluate the implications of this variability for human exposure assessments, focusing on cadmium (Cd) and lead (Pb) in lettuce and potatoes sampled around 22 contaminated glassworks sites. In addition, risks associated with measured Cd and Pb concentrations in soil and vegetable samples were characterized and a probabilistic exposure assessment was conducted to estimate the likelihood of local residents exceeding tolerable daily intakes. The results show that concentrations in vegetables were only moderately elevated despite high concentrations in soil, and most samples complied with applicable foodstuff legislation. Still, the daily intake of Cd (but not Pb) was assessed to exceed toxicological thresholds for about a fifth of the study population. Bioconcentration factors were found to vary more than indicated by previous studies, but decreasing BCFs with increasing metal concentrations in the soil can explain why the calculated exposure is only moderately affected by the choice of BCF value when generic soil guideline values are exceeded and the risk may be unacceptable. - Highlights: • Uptake of Cd and Pb by lettuce and potatoes increased with soil contamination. • Consumption of homegrown vegetables may lead to a daily Cd intake above TDIs. • The variability in the calculated BCFs is high when compared to previous studies. • Exposure assessments are most sensitive to the choice of BCFs at low contamination.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2019

Atomic-Level Insight into the Postsynthesis Band Gap Engineering of a Lewis Base Polymer Using Lewis Acid Tris(pentafluorophenyl)borane

Here, we investigate the binding properties of the Lewis acid tris(pentafluorophenyl)borane with a Lewis base semiconducting polymer, PFPT, and the subsequent mechanism of band gap reduction. Experiments and quantum chemical calculations confirm that the formation of a Lewis acid adduct is energetically favorable (ΔG° < -0.2 eV), with preferential binding at the pyridyl nitrogen in the polymer backbone over other Lewis base sites. Upon adduct formation, ultraviolet photoelectron spectroscopy indicates only a slight decrease in the HOMO energy, implying that a larger reduction in the LUMO energy is primarily responsible for the observed optical band gap narrowing (ΔE opt = 0.3 eV). Herein, we also provide the first spatially resolved picture of how Lewis acid adducts form in heterogeneous, disordered polymer/tris(pentafluorophenyl)borane thin films via one- (1D) and two-dimensional (2D) solid-state nuclear magnetic resonance. Notably, solid-state 1D 11 B, 13 C{ 1 H}, and 13 C{ 19 F} cross-polarization magic-angle spinning (CP-MAS) NMR and 2D 1 H{ 19 F} and 1 H{ 1 H} correlation NMR analyses establish that BCF molecules are intercalated between branched C 16 H 33 side chains with the boron atom facing toward the pyridyl nitrogen atoms of PFPT.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

A Thermodynamic and Kenetic Study of the Heterolytic Activation of Hydrogen by Frustrated Borane-Amine Lewis Pairs

Calorimetry is used to measure the reaction enthalpies of hydrogen activation by 2,6-lutidine (Lut), 2,2,6,6-tetramethylpiperidine (TMP), N-methyl-2,2,6,6-tetramethylpiperidine (MeTMP) and tri-tert-butylphosphine (TBP) with tris(pentafluorophenyl)borane (BCF). At 6.6 bar H2 the conversion of the Lewis acid Lewis base pair to the corresponding ionic pair in bromobenzene at 294 K was quantitative in under 60 minutes. Integration of the heat release from the reaction of the Frustrated Lewis Pair (FLP) with hydrogen as a function of time yields a relative rate of hydrogenation in addition to the enthalpy of hydrogenation. The half-lives of hydrogenation range from 230 seconds with TMP, ΔHH2 = -31.5(0.2) kcal/mol, to 1400 seconds with Lut, ΔHH2 = -23.4(0.4) kcal/mol. The 11B NMR spectrum of B(C6F5)3 in bromobenzene exhibits three distinct traits depending on the sterics of the Lewis base; (i) in the presence of pyridine, only the dative bond adduct pyridine--B(C6F5)3 is observed, (ii) in the presence of TMP and MeTMP only the free B(C6F5)3 is observed, and (iii) in the presence of Lut both the free B(C6F5)3 and the Lut--B(C6F5)3 adduct appear in equilibrium. A measure of the change in Keq of Lut + B(C6F5)3 <->Lut--B(C6F5)3 as a function of temperature provides thermodynamic properties of the Lewis acid Lewis base adduct, ΔH = -17.9(1.0) kcal/mol and a ΔS = -49.2(2.5) cal/mol K, suggesting the Lut--B(C6F5)3 adduct is more stable in bromobenzene than in toluene. This research was supported by the U.S. Department of Energy’s Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. D.M.C. and A.K. acknowledges support by the Laboratory Directed Research and Development program at the Pacific Northwest National Laboratory (PNNL) to perform kinetic analyses of the calorimetry data. The work was performed in part at EMSL, a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research. EMSL is located at Pacific Northwest National Laboratory (PNNL), which is operated by Battelle for DOE.

calorimetry↗

DOE OSTI2015

The importance of retaining a phylogenetic perspective in traits-based community analyses

1) Many environmental stressors manifest their effects via physiological processes (traits) that can differ significantly among species and species groups. We compiled available data for three traits related to the bioconcentration of the toxic metal cadmium (Cd) from 42 aquatic insect species representing orders Ephemeroptera (mayfly), Plecoptera (stonefly), and Trichoptera (caddisfly). These traits included the propensity to take up Cd from water (uptake rate constant, ku), the ability to excrete Cd (efflux rate constant, ke), and the net result of these two processes (bioconcentration factor, BCF). 2) Ranges in these Cd bioaccumulation traits varied in magnitude across lineages (some lineages had a greater tendency to bioaccumulate Cd than others). Overlap in the ranges of trait values among different lineages was common and highlights situations where species from different lineages can share a similar trait state, but represent the high end of possible physiological values for one lineage and the low end for another. 3) Variance around the mean trait state differed widely across clades, suggesting that some groups (e.g., Ephemerellidae) are inherently more variable than others (e.g., Perlidae). Thus, trait variability/lability is at least partially a function of lineage. 4) Akaike information criterion (AIC) comparisons of statistical models were more often driven by clade than by other potential biological or ecological explanation tested. Clade-driven models generally improved with increasing taxonomic resolution. 5) Altogether, these findings suggest that lineage provides context for the analysis of species traits, and that failure to consider lineage in community-based analysis of traits may obscure important patterns of species responses to environmental change.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2012

Dosimetric performance and array assessment of plastic scintillation detectors for stereotactic radiosurgery quality assurance

Purpose: To compare the performance of plastic scintillation detectors (PSD) for quality assurance (QA) in stereotactic radiosurgery conditions to a microion-chamber (IC), Gafchromic EBT2 films, 60 008 shielded photon diode (SD) and unshielded diodes (UD), and assess a new 2D crosshair array prototype adapted to small field dosimetry. Methods: The PSD consists of a 1 mm diameter by 1 mm long scintillating fiber (BCF-60, Saint-Gobain, Inc.) coupled to a polymethyl-methacrylate optical fiber (Eska premier, Mitsubishi Rayon Co., Ltd., Tokyo, Japan). Output factors (S{sub c,p}) for apertures used in radiosurgery ranging from 4 to 40 mm in diameter have been measured. The PSD crosshair array (PSDCA) is a water equivalent device made up of 49 PSDs contained in a 1.63 cm radius area. Dose profiles measurements were taken for radiosurgery fields using the PSDCA and were compared to other dosimeters. Moreover, a typical stereotactic radiosurgery treatment using four noncoplanar arcs was delivered on a spherical phantom in which UD, IC, or PSD was placed. Using the Xknife planning system (Integra Radionics Burlington, MA), 15 Gy was prescribed at the isocenter, where each detector was positioned. Results: Output Factors measured by the PSD have a mean difference of 1.3% with Gafchromic EBT2 when normalized to a 10 x 10 cm{sup 2} field, and 1.0% when compared with UD measurements normalized to the 35 mm diameter cone. Dose profiles taken with the PSD crosshair array agreed with other single detectors dose profiles in spite of the presence of the 49 PSDs. Gamma values comparing 1D dose profiles obtained with PSD crosshair array with Gafchromic EBT2 and UD measured profiles shows 98.3% and 100.0%, respectively, of detector passing the gamma acceptance criteria of 0.3 mm and 2%. The dose measured by the PSD for a complete stereotactic radiosurgery treatment is comparable to the planned dose corrected for its SD-based S{sub c,p} within 1.4% and 0.7% for 5 and 35 mm diameter cone, respectively. Furthermore, volume averaging of the IC can be observed for the 5 mm aperture where it differs by as much as 9.1% compared to the PSD measurement. The angular dependency of the UD is also observed, unveiled by an under-response around 2.5% of both 5 and 35 mm apertures. Conclusions: Output Factors and dose profiles measurements performed, respectively, with the PSD and the PSDCA were in agreement with those obtained with the UD and EBT2 films. For stereotactic radiosurgery treatment verification, the PSD gives accurate results compared to the planning system and the IC once the latter is corrected to compensate for the averaging effect of the IC. The PSD provides precise results when used as a single detector or in a dense array, resulting in a great potential for stereotactic radiosurgery QA measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2014

WE-E-18A-08: Towards a Next-Generation Electronic Portal Device for Simultaneous Imaging and Dose Verification in Radiotherapy

Purpose: This work forms part of an ongoing study to develop a next-generation electronic portal imaging device (EPID) for simultaneous imaging and dose verification in radiotherapy. Monte Carlo (MC) simulations were used to characterize the imaging performance of a novel EPID that has previously been demonstrated to exhibit a water-equivalent response. The EPID ' s response was quantified in several configurations and model parameters were empirically validated against experimental measurements. Methods: A MC model of a novel a-Si EPID incorporating an array of plastic scintillating fibers was developed. Square BCF-99-06A scintillator fibers with PMMA cladding (Saint-Gobain Crystals) were modelled in a matrix with total area measuring 150×150 mm{sup 2}. The standard electromagnetic and optical physics Geant4 classes were used to simulate radiation transport from an angled slit source (6 MV energy spectrum) through the EPID and optical photons reaching the photodiodes were scored. The prototype's modulation transfer function (MTF) was simulated and validated against experimental measurements. Several optical transport parameters, fiber lengths and thicknesses of an air gap between the scintillator and photodiodes were investigated to quantify their effects on the prototype's detection efficiency, sensitivity and MTF. Results: Simulated EPID response was more sensitive to variations in geometry than in the optical parameters studied. The MTF was particularly sensitive to the introduction of a 0.5–1.0 mm air gap between the scintillator and photodiodes, which lowered the MTF relative to that simulated without the gap. As expected, increasing the fiber length increased the detector efficiency and sensitivity while decreasing the MTF. Conclusion: A model of a novel water-equivalent EPID has been developed and benchmarked against measurements using a physical prototype. We have demonstrated the feasibility of this new device and are continuing to optimize the design to achieve an imaging response that warrants the development of a next-generation prototype.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2014

TH-C-19A-10: Systematic Evaluation of Photodetectors Performances for Plastic Scintillation Dosimetry

Purpose: To assess and compare the performance of different photodetectors likely to be used in a plastic scintillation detector (PSD). Methods: The PSD consists of a 1 mm diameter, 10 mm long plastic scintillation fiber (BCF-60) which is optically coupled to a clear 10 m long optical fiber of the same diameter. A light-tight plastic sheath covers both fibers and the scintillator end is sealed. The clear fiber end is connected to one of the following six studied photodetectors: two polychromatic cameras (one with an optical lens and one with a fiber optic taper replacing the lens); a monochromatic camera with the same optical lens; a PIN photodiode; an avalanche photodiode (APD); and a photomultiplier tube (PMT). Each PSD is exposed to both low energy beams (120, 180, and 220 kVp) from an orthovoltage unit, and high energy beams (6 MV and 23 MV) from a linear accelerator. Various dose rates are explored to identify the photodetectors operating ranges and accuracy. Results: For all photodetectors, the relative uncertainty remains under 5 % for dose rates over 3 mGy/s. The taper camera collects four times more signal than the optical lens camera, although its standard deviation is higher since it could not be cooled. The PIN, APD and PMT have higher sensitivity, suitable for low dose rate and out-of-field dose monitoring. PMT's relative uncertainty remains under 1 % at the lowest dose rate achievable (50 μGy/s), suggesting optimal use for live dosimetry. Conclusion: A set of 6 photodetectors have been studied over a broad dose rate range at various energies. For dose rate above 3 mGy/s, the PIN diode is the most effective photodetector in term of performance/cost ratio. For lower dose rate, such as those seen in interventional radiology, PMTs are the optimal choice. FQRNT Doctoral Research Scholarship.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Systematic evaluation of photodetector performance for plastic scintillation dosimetry

Purpose: The authors’ objective was to systematically assess the performance of seven photodetectors used in plastic scintillation dosimetry. The authors also propose some guidelines for selecting an appropriate detector for a specific application. Methods: The plastic scintillation detector (PSD) consisted of a 1-mm diameter, 10-mm long plastic scintillation fiber (BCF-60), which was optically coupled to a clear 10-m long optical fiber of the same diameter. A light-tight plastic sheath covered both fibers and the scintillator end was sealed. The clear fiber end was connected to one of the following photodetectors: two polychromatic cameras (one with an optical lens and one with a fiber optic taper replacing the lens), a monochromatic camera with an optical lens, a PIN photodiode, an avalanche photodiode (APD), or a photomultiplier tube (PMT). A commercially available W1 PSD was also included in the study, but it relied on its own fiber and scintillator. Each PSD was exposed to both low-energy beams (120, 180, and 220 kVp) from an orthovoltage unit and high-energy beams (6 and 23 MV) from a linear accelerator. Various dose rates were tested to identify the operating range and accuracy of each photodetector. Results: For all photodetectors, the relative uncertainty was less than 5% for dose rates higher than 3 mGy/s. The cameras allowed multiple probes to be used simultaneously, but they are less sensitive to low-light signals. The PIN, APD, and PMT had higher sensitivity, making them more suitable for low dose rate and out-of-field dose monitoring. The relative uncertainty of the PMT was less than 1% at the lowest dose rate achieved (0.10 mGy/s), suggesting that it was optimal for use in live dosimetry. Conclusions: For dose rates higher than 3 mGy/s, the PIN diode is the most effective photodetector in terms of performance/cost ratio. For lower dose rates, such as those seen in interventional radiology or high-gradient radiotherapy, PMTs are the optimal choice.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

TH-CD-BRA-12: Impact of a Magnetic Field On the Response From a Plastic Scintillation Detector

Purpose: To study the effect of a strong magnetic field on the scintillation and the stem effect from a plastic scintillation detector (PSD) and evaluate its accuracy to measure dose. Methods: A plastic scintillation detector and a bare plastic fiber were placed inside a magnet of adjustable field strength (B=0−1.5T) and irradiated by a 6-MV photon beam (Elekta Versa HD LINAC). The PSD was built in-house using a scintillating fiber (BCF-60, 3-mm long × 1-mm diameter) coupled to an optical fiber similar to the bare fiber (PMMA, 12-m long, 1-mm diameter). Light output spectra were acquired with a spectrometer. Intensity and shape of the output spectra were compared as a function of the magnetic field strength. The bare fiber was used to study the behavior of the stem effect (composed of Cerenkov and fluorescence). The spectrometry setup allowed to perform a previously demonstrated hyperspectral stem-effect removal and calculated dose was studied as a function of the magnetic field strength. Results: Signal intensities were shown to increase with the magnetic field strength by up to 19% and 79% at 1.5T in comparison to the irradiation without a magnetic field, for respectively the PSD and the bare fiber. The light produced by Cerenkov effect in the optical fiber was shown to be the major component affected by the magnetic field. Effect of the magnetic field on the electrons trajectory may explain this behavior. Finally, accounting for the stem effect using the hyperspectral approach led to accuracy in dose measurement within 2.6%. Interestingly, variations in accuracy were negligible for values over 0.3T. Conclusion: Dependence of PSDs to magnetic field is mainly due to the Cerenkov light. When accounting for it, PSDs become a candidate of choice for both quality assurance and in vivo dosimetry of therapy under strong magnetic fields (e.g. for MRI-Linacs).

60 APPLIED LIFE SCIENCES↗

DOE OSTI2012

Carbon Dioxide Storage and Utilization near Mingo County, West Virginia

Six oil fields within 100 miles of the planned coal-to-liquids facility in Mingo County were found to be prospective for miscible CO 2 -EOR. Four of the oil fields fall along a straight line and could, in concept, be developed sequentially along a single CO 2 pipeline. The total demand for purchased CO 2 from these four fields is estimated to be 47 million metric tons (890 Bcf) over 20 years. Four saline formations within Mingo County could accommodate 50 million metric tons of CO 2 (accounts for uncertainty and a &'buffer zone”). The combined storage capacity – EOR within 100 miles of Mingo County and saline within Mingo County – can accommodate 3 million metric tons per year of vented CO 2 for over 30 years Conclusion: there is enough potential for CO 2 utilization and storage that a next level of study is a reasonable course.

03 NATURAL GAS↗

NASA NTRS2004

Numerical Simulation of Nanostructure Growth

Nanoscale structures, such as nanowires and carbon nanotubes (CNTs), are often grown in gaseous or plasma environments. Successful growth of these structures is defined by achieving a specified crystallinity or chirality, size or diameter, alignment, etc., which in turn depend on gas mixture ratios. pressure, flow rate, substrate temperature, and other operating conditions. To date, there has not been a rigorous growth model that addresses the specific concerns of crystalline nanowire growth, while demonstrating the correct trends of the processing conditions on growth rates. Most crystal growth models are based on the Burton, Cabrera, and Frank (BCF) method, where adatoms are incorporated into a growing crystal at surface steps or spirals. When the supersaturation of the vapor is high, islands nucleate to form steps, and these steps subsequently spread (grow). The overall bulk growth rate is determined by solving for the evolving motion of the steps. Our approach is to use a phase field model to simulate the growth of finite sized nanowire crystals, linking the free energy equation with the diffusion equation of the adatoms. The phase field method solves for an order parameter that defines the evolving steps in a concentration field. This eliminates the need for explicit front tracking/location, or complicated shadowing routines, both of which can be computationally expensive, particularly in higher dimensions. We will present results demonstrating the effect of process conditions, such as substrate temperature, vapor supersaturation, etc. on the evolving morphologies and overall growth rates of the nanostructures.

Hwang, Helen H.↗

NASA NTRS2020

Creating High Temperature Ferroelectrics by Using Ternary Components with Limited Solubility

High temperature ferroelectrics are needed for actuator applications ranging from drilling on the surface of Venus to fuel modulation in jet engines. Machine learning in previous work has dramatically reduced search space and produced new candidates for experimentation. It is possible to create high temperature piezoelectrics by changing the end member of ternary systems. The starting point was near the morphotropic phas boundary between BiScO3(BS) and PbTiO3 (PT) (38%/62%). The third end member was suggested by machine learning to create a high Tc with limited solubility; BiCo0.88Fe0.12O3 (BCF).

Hirt, Benjamin↗

DOE OSTI2018

Iterated Discontinuity Factors Based on Reference Outgoing Currents for Discontinuous Finite Element Diffusion

We present a novel formulation for iteratively computing Discontinuity Factors (DF) designed to reproduce reference partial outgoing currents at the interface between macro-regions using Discontinuous Galerkin Finite Elements to solve the multigroup neutron diffusion equation. Similarly, an expression for the boundary coefficients (BCf) is proposed to match the partial outgoing current at vacuum boundaries. Upon convergence, macro-region averaged reaction and leakage rates are preserved. In addition, we consider a source-free steady-state problem depending on the DFs. The existence of a non-trivial solution is due to the non-linearity of the problem. This form greatly simplifies the implementation within Rattlesnake and efficiently converges by updating the DFs and BCfs at every linear iteration of the Preconditioned Jacobian-Free Newton-Krylov solver. The main challenge then lies in determining an appropriate scaling factor to ensure that the initial values for the DFs and BCfs are not too far from their converged value. While this factor does not change the final solution, it has the potential to significantly affect convergence, for purely numerical reasons. An expression based on the reference fission source integral is proposed and satisfying results are presented for problems and compared to Superhomogénéisation (SPH) results with both reflecting and vacuum boundary conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2018

Iterated Discontinuity Factors Based on Reference Outgoing Currents for Discontinuous Finite Element Diffusion

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2020

Testing Rod Seal Leakage of a 700 HP Reciprocating Compressor

Methane emissions from reciprocating compressors in the U.S. natural gas industry account for over 72.4 Bcf per year according to a 2006 statement by the United States Environmental Protection Agency. Methane also has a global warming potential 50 times greater than carbon monoxide. Reciprocating compressors are the machinery type with the highest contribution to methane emissions at natural gas transmissions stations. The largest contributing factor comes from the sealing components in the packing components around the piston rod. SwRI, therefore, designed and setup a test loop to perform baseline packing leakage measurements on a four stage 700 HP JGT/4 compressor. The goal was to improve upon current packing leakage models and to compare new seals vs. used seals. The test loop design is described including the limits of operation. The Data Acquisition System (DAQ), including data measurements, is also fully described. The project shows the results of the commissioning process that verified the operation of all the components. Once the loop was commissioned, SwRI performed baseline packing leakage for multiple pressure ratios on each of the four stages of the compressor. The data was collected to develop an analytical model of the packing leakage. Finally, similar testing was performed after replacing the typical rod seal packing with used packing. The used packing leakage was compared to the baseline packing leakage.

03 NATURAL GAS↗